PROJECT SUMMARY Chronic musculoskeletal (MSK) conditions, such as low back pain, hip or knee osteoarthritis are the primary cause of disability in mid-life and older adults in the United States. Individuals living with chronic MSK conditions often have trouble being physically active and experience a downward spiral in health and quality-of-life due to the consequences of the pain and disability. Physical therapy (PT) is an important component of treatment for MSK conditions. PT could also be an optimal environment in which to implement physical activity (PA) interventions and disrupt the downward spiral. PA increases during an episode of routine PT care but these changes fail to be sustained. This represents a missed opportunity to teach individuals how to improve health behaviors and maintain them after discharge. Behavioral theories provide theoretical explanations on the social-cognitive process in health-behavior change. The Health Action Process Approach (HAPA) is a two-layered behavior model that helps to explain the transition from goal setting (motivation) to goal pursuit (volition). The objective of this application is to understand the degree to which routine PT influences PA using the HAPA framework and to identify barriers to supporting changes in PA. Specific aims are to (1) evaluate changes in PA motivation within an episode of routine PT care and the correlation between motivation and disability, (2) evaluate changes in PA volition within and episode of routine PT care and the correlation with PA, and (3) identify clinician-level factors the promote or hinder supporting patients in changing PA behaviors. We hypothesize that specific barriers must be addressed to help patients move from PA motivation to PA volition and there is a gap in this delivery. We will conduct a mixed methods study within routine PT clinical practice. We will measure changes in PA motivation and volition in mid-life and older adults with chronic MSK conditions before and after routine PT care. Using semi-structured interviews, we will ask physical therapists to identify factors that promote or hinder the delivery of interventions that would improve PA volition or sustained PA. We expect increased PA motivation over the PT episode of care that diminishes as patients are distanced from PT. We anticipate barriers to delivery include a lack of skills and time to deliver effective behavior change interventions. We also anticipate clinicians will support the promotion of PA and identify innovative interventions to improve PT care toward this end. With a focus on routine PT clinical care, this study will provide needed insights into the extent motivational and volitional constructs are delivered in PT. This data alongside insights from physical therapists will lead to development of a PA promotion intervention for trial within clinical practice.